Sets

Initializing sets (set, {,,,})

set([1, 2, "a"])

{1, 2, 'a'}

{1, 2, "a"}

{1, 2, 'a'}

set() # empty set

set()

{} # empty dictionary, not the empty set!

{}

Adding and deleting elements (.add, .remove, .discard, .pop, .clear)

s1 = {1, 2, 3, "a", "b"}
s2 = {2, 4, 6, "a", "c"}
s3 = {3, 33}
s1.add("d")
s1, s2, s3

({1, 2, 3, 'a', 'b', 'd'}, {2, 4, 6, 'a', 'c'}, {3, 33})

s1.remove("c")

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-6-72ce1ccfa9ab> in <module>
----> 1 s1.remove("c")

KeyError: 'c'

s1.discard("c") # no error message if the element is not in the set
s1

{1, 2, 3, 'a', 'b', 'd'}

s1.pop()   # delets one element and returns it

1

s1

{2, 3, 'a', 'b', 'd'}

Operations: union, update, intersection, isdisjoint, difference, symmetric_difference, |, &, -, ^,

s1.union(s2)  # returns the union, but does not change s1

{2, 3, 4, 6, 'a', 'b', 'c', 'd'}

s1

{2, 3, 'a', 'b', 'd'}

s1.update(s3) # update s1 with the union; s3 can be list, tuple...

s1

{2, 3, 33, 'a', 'b', 'd'}

s1 | s2

{2, 3, 33, 4, 6, 'a', 'b', 'c', 'd'}

s1 & s2

{2, 'a'}

s1 - s2

{3, 33, 'b', 'd'}

s1 ^ s2

{3, 33, 4, 6, 'b', 'c', 'd'}